Given that many natural resources (such as water, soil, forests and fish stocks) are already being exploited to or beyond their limits, in at least some regions, the efforts required to meet the needs of an additional 3 000 million people in the next 50 years will be immense, even at present consumption levels. If poverty is to be reduced and economic benefits distributed more equitably, then a further major increase in production will be required, not to mention significant modifications to economic, social and political systems. Whether the planetary environment can meet these demands, and under what conditions, is an open question.